# The Association Between Early Postoperative Temperature Trajectories and Severe Acute Kidney Injury After Valvular Heart Surgery: A Retrospective Cohort Study

## TL;DR

This study finds that early post-surgery temperature patterns are linked to severe kidney injury risks in heart surgery patients.

## Contribution

Identifies specific temperature trajectories post-surgery that are independently associated with severe acute kidney injury.

## Key findings

- Four distinct temperature trajectories were identified in postoperative patients.
- Lower-range mild hypothermia with delayed recovery (Class 4) was most strongly associated with severe AKI.
- Class 4 patients had significantly higher rates of non-recovery AKI compared to other classes.

## Abstract

Background/Objectives: Postoperative body temperature abnormalities are common yet underrecognized, and their association with acute kidney injury (AKI) remains unclear. In this study, we aimed to identify early postoperative temperature trajectories and evaluate their associations with AKI. Methods: This retrospective cohort study included 3274 adults undergoing valvular heart surgery with cardiopulmonary bypass. The patients’ temperatures were continuously measured using a pulmonary artery catheter for 12 postoperative hours, and temperature trajectories were identified using data-driven latrend class modeling. The primary outcome was severe AKI (KDIGO stage ≥ 2), and the secondary outcome was non-recovery AKI (≥72 h). Multivariable logistic regression and E-value sensitivity analysis were performed. Results: Four distinct temperature trajectories were identified: Class 1 (32.8%), initial normothermia progressing to mild hyperthermia (37.5–38.0 °C); Class 2 (27.4%), mild hypothermia (36.0–36.5 °C) with rapid normalization; Class 3 (24.4%), stable normothermia; and Class 4 (15.4%), lower-range mild hypothermia (35.5–36.0 °C) with delayed recovery. Severe AKI and non-recovery AKI occurred most frequently in Class 4 patients (15.1% vs. 2.9%, 3.9%, and 4.8% in Classes 1–3, p < 0.001; 15.1% vs. 1.7%, 4.0%, and 4.4%, p < 0.001, respectively). After adjusting for key clinical variables, Class 4 remained independently associated with severe AKI (OR 2.44, 95% CI: 1.69–3.57; E-value 4.33) and non-recovery AKI (OR 2.78, 95% CI: 1.89–4.00; E-value 4.97). Conclusions: Early postoperative temperature trajectories were significantly associated with severe AKI, with the highest risks in patients exhibiting lower-range mild hypothermia with delayed recovery. These findings suggest that early postoperative temperature patterns may be useful for risk stratification for severe AKI after cardiac surgery.